Marine Weather and Tide Forecast for Chatham, MI

DISCUSSION
Issued at 225 AM EST Tue Nov 11 2025

Upper Michigan finds itself under mid-level ridging building across the region ahead of a weakly forced shortwave pressing through Minnesota and western Ontario. Radar returns in Minnesota within this region of isentropic ascent have only yielded a single observation of precip reaching the surface thanks to dry low levels.
Ahead of this region over Upper Michigan, ridging has resulted in diminishing lake effect snow showers. Current shower activity is limited to isolated showers moving into Luce County. Temperatures have been observed mostly in the 20s, save for low 30s by Lake Superior and in the Keweenaw.

An outgoing upper level low will continue digging eastward into the Mid-Atlantic/Northeast today while upstream mid to upper level ridging holds across western CONUS. This positions the forecast area largely in northwest flow aloft and under the influence of any waves dropping southeast through Canada or the Northern Plains through Thursday when the next wave presses into the west coast, resulting in the downstream ridging to begin migrating eastward into the middle North America. Today, the upstream wave extending northward through Minnesota will continue to dive southeast. As mentioned earlier though, moisture will be the main limitation for any significant precipitation this morning along the surface trough. As the day progresses, the shortwave will approach from the northwest which will provide additional forcing to overcome the dry low levels across the east. This should result in light rain or snow showers by afternoon, mainly east of Munising. Snow accumulations are not expected given daytime temperatures climbing into the upper 30s to low 40s in the east. Elsewhere, mid 30s to low 40s are expected.

Cold air advection behind the surface trough will bring 850mb temps down to around -6C. With Lake Superior surface temps still running from +6 to +9C per GLERL analysis, another lake effect episode is expected to develop into Thursday. Model soundings show inversion heights climbing to near 7k feet, but barely dig into the DGZ.
Additionally, drier low levels and low level wind shear should limit snow accumulations in this episode. Tonight any snow should amount to half an inch or less and be limited to mainly the higher terrain of the Gogebic Range and Michigamme Highlands and the snow belts east of Seney. Wednesday into Thursday, any precip during daytime hours should transition to light rain given temperatures warming into the upper 30s to mid 40s. Shower activity will also diminish in the west by late Wednesday, then diminish late Thursday in the east, thanks to increasing ridging slowly building into the region. The tighter pressure gradient and cold air advection over the area tonight and Wednesday will also result in breezy northwest winds, especially near Lake Superior and in the Keweenaw where 35 to 40 mph gusts could be common. Some guidance does suggest 40+ mph potential in the Keweenaw Wednesday. Elsewhere Wednesday, gusts of 20-30mph should be expected.

Surface high will keep the region dry Friday. Warm air advection will also continue the warming trend, and the forecast area should warm into the mid to upper 40s. The same applies to Saturday, although slightly warmer conditions are expected under southerly flow. Next shot for precip begins sometime Saturday or Saturday night and could persist through the weekend as the associated trough moves slowly from the Northern Plains through the Great Lakes.

Temperatures are anticipated to warm above freezing this week, then fall below freezing overnight. Any snow that melts during the day will refreeze overnight. This may result in ice or black ice on roadways, which could impact the morning commutes Wednesday and Thursday.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
Issued at 639 AM EST Tue Nov 11 2025

VFR conditions are observed at all TAF sites this morning. Ceiling heights will begin to descend today to low-end VFR with CMX being the first to descend into MVFR ceilings this evening as a lake effect regime sets up once again. With WSW winds forecast, IWD and SAW are only 25-40 percent likely to see showers while CMX is up to 70 percent likely to see showers overnight. With a warmer airmass than earlier in the week, these showers will fall as either -SHRASN or all -SHRA. CMX is 50-60% likely to have a period of IFR conditions overnight while IWD and SAW are only 30-40 percent likely to descend into IFR. Some recovery is possible around 12Z Wednesday, but more likely will occur after the TAF period.

MARINE
Issued at 225 AM EST Tue Nov 11 2025

Light winds have been observed across Lake Superior tonight save for southwest gusts approaching 20kts across parts of western Lake Superior. Southerly to southwesterly flow will establish itself lake-wide today and increase to 20-30kts ahead of a surface trough/cold front moving through the region. Cold air advection and a tighter pressure gradient will follow, which will result in westerly becoming northwesterly winds increasing to low end gales tonight through Wednesday. Main areas where these gales are likely are around the Keweenaw, but ensemble guidance suggests potential exists for most locations in central and eastern Lake Superior.
Opted to upgrade the inherited watch to a Gale Warning with this forecast package. Latest WW3 continues to suggest significant waves over the west half climbing to 4-8 ft and 8-14 ft over the east (highest north of Grand Marais, MI).

Winds are expected to settle below gale late tonight, but suspect gale force gusts could continue into Thursday afternoon north and east of the Keweenaw. Thursday evening, winds look to return below 20kts lake-wide and remain there into Friday afternoon. From there, southeasterly flow becoming southerly under increasing gradient forces late Friday into Saturday will result in winds climbing to 20- 30kts ahead of the next system. Potential exists for this warm air advection pattern to reach gales north and east of the Keweenaw given the modeled 35-40kt 925mb LLJ, but latest NBM and EC ensemble currently pings potential at 20-40%, at least until Saturday night/Sunday. At that point, northwest flow could gradually develop behind the departing system alongside a slug of stronger cold air advection. Should this occur, gales would be favored Sunday into Monday.

MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
None.
Lake Superior...
Gale Warning from 1 AM EST /midnight CST/ to 7 PM EST /6 PM CST/ Wednesday for LSZ241-242-263.

Gale Warning from 1 AM Wednesday to 1 AM EST Thursday for LSZ243>251-264>267.

Lake Michigan...
None.